The causal chain feels like a post-justification and not what actually goes on in the child's brain. I expect this to be computed using a vaguer sense of similarity that often ends up agreeing with causal chains (at least good enough in domains with good feedback loops). I agree that causal chains are more useful models of how you should think explicitly about things, but it seems to me that the purpose of these diagrams is to give a memorable symbol for the bug described here (use case: recognize and remember the applicability of the technique).